Field of the Invention
The present invention relates to a technique of a rotary lawn mower for cutting lawn grass by a cutter blade accommodated in a housing.
Description of the Related Art
The rotary lawn mower cuts (clips) lawn grass by rotating a cutter blade accommodated in a housing having an opened bottom, along lawn grass to cut the lawn grass. As a technique of such a lawn mower, for example, U.S. Pat. No. 7,275,355 is known.
The lawn mower known in U.S. Pat. No. 7,275,355 includes a housing having an opened bottom, a rotation shaft positioned inside the housing and extending in a vertical direction of the housing, and a cutter blade accommodated in the housing in a manner that the cutter blade is rotatable about the rotation shaft. The lawn grass (grass clippings) cut by the cutter blade is lifted upward, and swirled in the housing by the air lifts, and then, transported into a grass clippings container.
A belt type continuously variable transmission is provided in a working power transmission system from the drive source to the rotation shaft. This belt type continuously variable transmission includes a drive pulley provided for the drive source, a driven pulley provided for the rotation shaft, and a belt hooked between these pulleys. The driven pulley includes a fixed sheave provided for the rotation shaft, a movable sheave which is displaceable relative to the fixed sheave in an axial direction, and a device for driving the driven pulley to move closer to the drive pulley. This device is a mechanism which moves in a linear fashion such as a solenoid or a linear actuator, and the device is controlled by a control unit. This control unit can control the rotation speed of the cutter blade by controlling the device in accordance with various factors such as a lawn mowing load applied to the cutter blade.